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Validating a narrow codend cover and improving selectivity in south-eastern Australian fish trawls targeting eastern school whiting, Sillago flindersi
Fisheries Research ( IF 2.2 ) Pub Date : 2022-03-17 , DOI: 10.1016/j.fishres.2022.106302
Matt K. Broadhurst 1, 2 , Russell B. Millar 3
Affiliation  

As part of attempts to improve selection among south-eastern Australian benthic fish trawls, an experiment was done to assess: (1) for confounding effects of a narrower-than-recommended hooped cover over a conventional trawl codend; and then (2) the associated size selection of eastern school whiting, Sillago flindersi; and (3) if this could be improved by inserting a large panel of smaller square-shaped mesh. The narrow cover was required to avoid contacting the seabed and did not affect trawl wing-end spread or catching efficiency. Despite a stretched mesh opening (SMO) of 96 mm and much larger than all S. flindersi (11–26 cm total length; TL), the conventional codend had a low 50% size at retention (L50) of 16.8 cm TL (selection range of 5.9 cm), which was close to the minimum marketable length. The capture of small S. flindersi by the large-meshed codend was attributed to an excessive increase in circumference (from 100 to 200 meshes) and a legally permitted ‘catch-separating’ rope to restrict fractional mesh openings to <~21%. Replacing ~1/4 of the 96-mm SMO netting in the codend and anterior extension with a panel of square-shaped mesh (~42-mm SMO hung on the bar) marginally (p = 0.065) improved size selection for S. flindersi (by allowing some fish <~15 cm TL to escape). Increasing the size of mesh in the panel to ~47 mm hung on the bar might allow more smaller S. flindersi to escape. But using a smaller mesh size throughout the entire codend, concurrent with other gear or spatio-temporal controls when targeting S. flindersi might be a more coherent management option than retroactively handicapping the existing large-mesh codends.



中文翻译:

验证狭窄的密码覆盖范围并提高澳大利亚东南部鱼拖网针对东部学校鳕鱼 Sillago flindersi 的选择性

作为改善澳大利亚东南部底栖鱼拖网选择的尝试的一部分,进行了一项实验以评估:(1)比推荐的环盖窄于传统拖网编码的混杂影响;然后(2)东部学校鳕鱼、Sillago flindersi的相关尺寸选择;(3) 是否可以通过插入一大块较小的方形网格来改善这种情况。要求狭窄的覆盖物避免接触海床,并且不影响拖网翼端展开或捕获效率。尽管拉伸网孔 (SMO) 为 96 毫米,并且比所有S. flindersi (11-26 厘米总长度; TL) 大得多,但传统的 codend 在保留时具有低 50% 的尺寸 (L 50) 的 16.8 厘米 TL(选择范围为 5.9 厘米),接近最小可销售长度。大网眼密码对小型S. flindersi的捕获归因于周长过度增加(从 100 到 200 目)和法律允许的“捕获分离”绳索,以将分数网格开口限制在 <~21%。用方形网片(约 42 毫米 SMO 挂在杆上)略微 ( p = 0.065) 改进S. flindersi 的尺寸选择(通过允许一些 <~15 cm TL 的鱼逃脱)。将面板中的网格尺寸增加到悬挂在杆上的 ~ 47 mm 可能会允许更小的S. flindersi逃离。但是,在针对S. flindersi时,在整个 codend 中使用较小的网格尺寸,与其他齿轮或时空控制同时进行,可能是比追溯限制现有的大网格 codends 更连贯的管理选项。

更新日期:2022-03-17
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